Headphones for the hard of hearing?

This may seem like an odd request, but I have a friend who has very little hearing (can hear concerts/engines etc...) is there anything he can buy < $100 headphone wise to let him hear music. Kinda want to avoid the whole everyone around him hearing his music too (so closed).

I'm not sure what to recommend him as I have never been in the market for something like this. I'm not sure if there are any headphones that will even go loud enough for his needs.

In the tests performed to test hearing as well as testing the ability of the ears to hear noise

electrodes are attached to the BONE structure behind the ear.

to test the hearing through the bone structure. Therefore transducers attached there could input music to the brain via whats left of your hearing[conductive hearing test]-testing the INNER ear capacity to hear.

You could therefore make or I am sure I am not the only one to think of this be able to buy a product like that.

In WW2 US forces used throat microphones to communicate.

If there isn't a commercial producer then ex-WD electronic supplies could sell something that could be converted

Even-dare I say it - US security forces.-maybe selling off old technology.

Nobody is going to hear that even how loud it goes.

Yes -FR will be way out-BUT we are talking of listening to music while on the move and in company and that would work.

And it wont effect whats left of your hearing.

This isn't "hard technology"-If nobody sells it then maybe I could produce a working model if I can obtain the